Process for the recovery of niobium



United States Patent 3,047,476 PRQQESS FOR THE RECOVERY OF NIOBIUM Fritz Kern, Therwil, Switzerland, assignor to Cilia Limited, Basel, Switzerland, a company oi Switzerland No Drawing. Filed Nov. 29, 1960, Ser. No. 72,274 Cls priority, application Switzerland Dec. 11, 1959 2 Qlaims. (Cl. 204-64) This invention provides a process for the recovery of niobium from mixtures of niobium and tantalum having a small content of tantalum.

Mixtures of niobium and tantalum having a ratio of tantalum to niobium smaller than 4:1 by weight frequently occur in nature in the form of columbites. There is also a large number of separating and concentrating processes in which such mixtures may be ob tained as by-products, for example, as intermediate fractions in chlorinating and extracting processes, selective chlorinations or selective precipitation processes. As such mixtures of niobium and tantalum generally have no practical importance, the problem arises of recovering from such mixtures at least one of the two constituents in as pure 3, form as possible.

The present invention provides a process for the recovery of niobium from mixtures of niobium and tantalum, in which the ratio by weight of tantalum to niobium is less than 3:1, wherein the said mixture, it it is not already a mixture of niobium and tantalum pentachlorides, is converted into a mixture of the pentachlorides, and the mixture of the pentachlorides is electrolyzed in an alkali metal fluoride melt, and the electrolysis is discontinued when the ratio by weight of tantalum to niobium in the melt is equal to or greater than 3:1.

The metallic niobium obtained by the electrolysis contains only a small proportion of tantalum. The separation effect brought about in the process of the invention is surprising and could not have been foreseen. It would rather have been expected that both metals would separate out. The process therefore constitutes a valuable contribution to the art of recovering the metals.

Pentachloride mixtures used as starting materials are mixtures of niobium pentachloride and tantalum pentachloride having a small content of tantalum. Advantageously there are used pentachloride mixtures obtained by'the chlorination of niobium-tantalum ores having a low content of tantalum. There may also be used as starting materials intermediate fractions obtained by other methods for separating niobium and tantalum, for example, distillation, extraction etc. These fractions may already be in the form of the pentachlorides, but if not gthey may be converted into a mixture of the pentachlo- Example 1 The electrolytic cell consisted of a graphite crucible having an internal diameter of 80 mm. and a depth of 210 mm., the graphite crucible being connected as the anode.

The nickel rod of 15 mm. in diameter was used as cathode. The entire apparatus was shut oil? from the atmosphere by means of a quartz crucible. The mixture of niobium pentachloride and tantalum pentachloride was introduced as a gas into a melt of 515 grams of N'aCl,

'285 grams of KCl and 400 grams of KP until the melt Percent by weight 98.3 1.7

Niobium Tantalum After the hydrolysis the melt contained 4.6% by weight I of tantalum and 1.6% by Weight of niobium.

When the melt was electrolyzed under the same conditions for a further 30 minutes, the metal powder obtained had the following composition:

Percent by weight Niobium 65.5 Tantalum 34.5

Example 2 In the electrolytic cell described in Example 1 a melt consisting of equal parts of an alkali metal chloride and an alkali metal fluoride having a content of 4.9% by weight of tantalum and 2.4% by weight of niobium, which corresponds to a ratio by weight of tantalum to niobium of approximately 2:1, was electrolyzed for 30 minutes at 60 amperes. There were obtained 13.3 grams of a metal powder having the following composition:

Percent by weight 91.4

After the electrolysis the melt contained 1.35% by weight of niobium and 4.7% of tantalum which corresponds to a ratio by weight of tantalum to niobium of 3.5:1.

What is claimed is:

1. A process for the recovery of niobium fiom mixtures of niobium pentachloride and tantalum pentachloride in which the ratio by weight of tantalum to niobium is less than 3:1, which comprises subjecting the mixture of pentachlorides to electrolysis in a melt of sodium chloride, potassium chloride and potassium fluoride, and discontinuing the electrolysis when the ratio by Weight of tantalum to niobium in the melt is substantially equal Niobium Tantalum References Cited in the file of this patent FOREIGN PATENTS Norway Mar. 3, 1952 Australia May 22, 1958 

1. A PROCESS FOR THE RECOVERY OF NIOBIUM FROM MIXTURES OF NIOBIUM PENTACHLORIDE AND TANTALUM PENTACHLORIDE IN WHICH THE RATIO BY WEIGHT OF TANTALUM TO NIOBIUM IS LESS THAN 3:1, WHICH COMPRISES SUBJECTING THE MIXTURE OF PENTACHLORIDES TO ELECTROLYSIS IN A MELT OF SODIUM CHLORIDE, POTASSIUM CHLORIDE AND POTASSIUM FLUORIDE, AND DISCONTINUING THE ELECTROLYSIS WHEN THE RATIO BY WEIGHT OF TANTALUM TO NIOBIUM IN THE MELT IS SUBSTANTIALLY EQUAL TO 3:1. 